A conventional heating appliance, such as a toaster or toaster oven, typically includes a plurality of bread guards positioned within a cooking cavity of the appliance. Each of the bread guards is positioned adjacent a corresponding heating element that generates heat to cook a food item placed within the cooking cavity during operation of the toaster. The bread guards function to prevent a food item placed in the toaster from directly contacting the heating elements. In many conventional toasters, the bread guards are also movable, and function to both prevent contact with the heating elements and to position the food item within the cooking cavity for optimum cooking.
FIG. 1 is an isometric view of a conventional toaster 400 with its external housing (not shown) removed to better illustrate a shell 300 including two side panels 302, 304, a rear panel 306, and two front sub panels 316 and 318. The panels 302-306 and 316, 318 may be separate components that are joined by suitable means, or the shell 300 may be a unitary structure. The toaster 400 includes first and second outer heating elements 402, 404 positioned inside the side panels 302 and 304, respectively. The heating elements 402, 404 include respective first electrical terminals 406, 408 extending through apertures 319, 321 in the front sub panels 316, 318, and respective second electrical terminals 410, 411 extending above a top edge of the rear panel 306. Each of the electrical terminals 406-411 is adapted to receive a respective power signal that is applied to circuitry (not shown) on the heating element 402, 404 to generate heat for toasting food items.
The toaster 400 further includes a movable outer bread guard 418 positioned inside the outer heating element 402, and a similar movable outer bread guard 420 positioned inside the outer heating element 404. The outer bread guard 418 includes a lower arm 422 having a front end that extends through a hook 324 in the sub panel 316 and a rear end that extends through a hole 427 in the rear panel 306 to thereby position the outer bread guard 418 in place. The outer bread guard 420 includes a lower arm 423 that is positioned in the same way through a hook 325 in the sub panel 318 and a hole (not shown) in the rear end panel 306. Each of the bread guards 418, 420 further includes an upper arm 419 and vertical members 421 as shown for the bread guard 418. A bottom bracket 426 is attached to the bottom of the front sub panels 316, 318 to secure each of the arms 422, 423 in the corresponding hooks 324, 325 as shown, and thereby secure the bread guards 418, 420 in place. A spring (not shown) is coupled between the lower arms 422, 423 and functions to move the outer bread guards 418, 420 to their desired positions during operation of the toaster 400, as will be described in more detail below.
A center heating element 412 is positioned between the outer heating elements 402 and 404, and includes a pair of terminals 414 that extend through an aperture in the rear panel 306. Two stationary inner bread guards 434 and 436 are positioned on respective sides of the center heating element 412. Each of the inner bread guards 434 and 436 is attached at its rear end through a corresponding tab on the rear panel 306, and is attached at its front end through a corresponding tab on a carriage support bracket 438 positioned between the front sub panels 316 and 318 and a tab on the bottom bracket 426. The toaster 400 further includes an electronic circuit 428 mounted on the horizontal portion of the bottom bracket 426. Although not shown in FIG. 1, the electronic circuit 428 is coupled to the terminals 406-411 and 414 of the heating elements 402, 404, and 412, and operates to control the toaster 400 during operation.
In the toaster 400, a first bread cavity 440 is defined between the bread guards 418 and 434, and a second bread cavity 442 is defined between the bread guards 420 and 436. A first bread tray (not shown) is contained within the first bread cavity 440 and functions to support a piece of bread as it is lowered into and raised from the bread cavity 440. A second bread tray (not shown) is similarly positioned within the second bread cavity 442 to support another piece of bread in the bread cavity 442. Each of the bread trays includes a lever 444 extending through slots 446 and 448, respectively, formed between the carriage support bracket 438 and the sub panels 318 and 316, respectively. The carriage support bracket 438 has a hole 439 adapted to receive a vertical rod (not shown). A bread carriage (not shown) is attached to the levers 444, and slides along the vertical rod to raise and lower the bread trays.
The operation of the movable bread guards 418 and 420 during operation of the toaster 400 will now be described in more detail with reference to the schematic diagrams of FIGS. 2A and 2B. FIGS. 2A and 2B schematically depict side views of the outer bread guard arms 418 and 420. A spring 450 is coupled between the lower bread guard arms 422 and 423 and functions to apply a force to these arms to move the bread guards 418 and 420 to a desired position, as will be explained in more detail below. A vertical rod 452 extends through adjacent a center portion of the spring 450, and the rod is mounted between the hole 439 in the carriage support bracket 438 and the bottom bracket 426, as previously described with reference to FIG. 1. A bread carriage 454 is attached to the levers 444, and slides along the rod 452 to raise and lower the bread trays during operation of the toaster 400. A first stop 456 is formed on the side panel 302 and a second stop 458 is formed on the side panel 304. The stops 456, 458 limit the inward movement of the bread guards 418, 420, as will be described in more detail below.
FIG. 2A depicts the bread carriage 454 and bread guards 418 and 420 when the toaster 400 is OFF and a return force F.sub.R is applied to the bread carriage 454 by, for example, a spring (not shown), causing the bread carriage 454 to slide towards the top of the rod 452. In this situation, the center portion of the spring 450 extends upward, and the spring 450 applies respective outward bias forces F.sub.OUT to the lower bread guard arms 422 and 423, thereby placing the bread guards 418 and 420 in their outward positions. Thus, in FIG. 2A, the bread carriage 454 is positioned near the top of the rod 452 and the bread guards 418 and 420 are positioned outward in anticipation of food items being placed on the bread supports and initiation of a heating cycle of the toaster 400.
FIG. 2B illustrates the bread carriage 454, spring 450, and bread guards 418 and 420 during a heating cycle of the toaster 400. To initiate a heating cycle, an external force is applied to the bread carriage 454, sliding the bread carriage toward the bottom of the rod 452. As the bread carriage 454 slides towards the bottom of the rod 452, it contacts the spring 450 and applies a force to the spring. In response to this force, the spring 450 flattens out as shown in FIG. 2B. As the spring 450 flattens out and moves from its position in FIG. 2A to that in FIG. 2B, it applies inward bias forces F.sub.IN to the lower bread guard arms 422 and 423. In response to the inward bias forces F.sub.IN, the bread guards 418 and 420 rotate about the axes of the arms 422, 423 to their inward positions. During a heating cycle, the bread carriage 454 is retained in its downward position by a retaining mechanism (not shown). Upon termination of a heating cycle, the retaining mechanism releases the bread carriage 454, which thereafter slides towards the top of the rod 452 in response to the return force F.sub.R as shown in FIG. 2A. When the bread carriage 454 slides upward, the spring 450 once again returns to its position shown in FIG. 2A thereby applying the forces F.sub.OUT to the bread guards 418 and 420 to place the bread guards in their outward position in anticipation of a subsequent heating cycle. The stops 456 and 458 prevent the bread guards 418 and 420 from rotating too far inward so that a food item may not inadvertently be placed directly against a heating element on the wrong side of one of the guards 418 and 420.
In the conventional toaster 400, each toaster must include the spring 450 coupled between the bread guard arms 422 and 423 in order to properly position the bread guards 418 and 420. As a result, each of the conventional toasters 400 must include at least one spring 450 to control the movable bread guards 418 and 420. The spring 450 can take many forms and may be attached to the bread guards in many different ways, as will be understood by those skilled in the art. Each spring 450 increases the cost of the toaster 400 due to the cost of the spring itself plus the labor required for installing the spring. As understood by those skilled in the art, the manufacturing volumes of conventional toasters may be very large, and thus the cost of the spring and the associated labor may result in the expenditures of large sums of money.
There is a need for a movable bread guard in the heating appliance that reduces the cost of and simplifies the installation of the bread guard to thereby reduce the overall cost of the appliance.